A process for treating a substrate with ethylene-maleic anhydride copolymer powder

ABSTRACT

A process for treating the surface of a material is provided which comprises treating the surface with a powder of a statistical copolymer of ethylene and maleic anhydride having a particle size of between 0.5 Mu and 400 Mu and possessing, in the dispersed state, on its particles, at least one crosslinking agent for the copolymer, which contains as reactive groups one, two, three or four alcoholic-OH groups and at least one amino or amido group, in an amount from 0.05 to 6 reactive groups per anhydride group present in the copolymer, and then bringing the powder to a temperature of between 110* and 300*C.

United States Patent n91 Fourment et a1.

[ 1 A PROCESS FOR TREATING A SUBSTRATE WITH ETllYLENE-MALEIC ANHYDRIDECOPOLYMER POWDER [75] Inventors: Marie-Claude GloriodNee Fourment,Bully-Les-Mines; Adrien Nicco, Bethune, both of France [73] Assignee:Ethylene P1astique,Courbevoie,

France [22] Filed: Mar. 24, 1972 [2]] Appl. No,: 237,915

[30] Foreign Application Priority Data Mar. 25, 1971 Great Britain7853/71 [52] US. Cl 117/21, 117/27, 117/104 R,

1 17/105.1,117/105.2,117/123 D, 117/132 C, 117/140 A, 117/155 R, 117/161UC, 117/124 E, 117/126 GB',117/141, 260/546 [51] Int. Cl B44d 1/02, B44d1/44 [58] Field of Search 117/21, 27,161 UC, 117/104 R, 105.1, 105.2,123 D, 132 C, 140 A, 155 R; 260/546 [56] References Cited UNITEDSTATESPATENTS 3,211,808 10/1965 Young et all. 117/161UC 1 Jan. 8, 1974Clock 117/21 Ravve et a1. 117/161 UC Primary ExaminerWilliam D. MartinAssistant ExaminerWi1liam R. Trenor Att0rney-Bacon & Thomas et a1.

57 ABSTRACT A process for treating the surface of a material is providedwhich comprises treating the surface with a powder of a statisticalcopolymer of ethylene and maleic anhydride having a particle size ofbetween 0.5 ,u. and 400 and possessing, in the dispersed state, on itsparticles, at least one crosslinking agent for the copolymer, whichcontains as reactive groups one, two, three or four alcoholic-OH groupsand at least one amino or amido group, in an amount from 0.05 to 6reactive groups per anhydride group present in the copolymer, and thenbringing the powder to a temperature of between 1 10 and 300C.

11 Claims, No Drawings 1 A PROCESS FOR TREATING A SUBSTRATE WITHETHYLENE-MALEIC ANHYDRIDE COPOLYMER POWDER The present invention relatesto a powder based on an ethylene maleic anhydride copolymer for thetreatment of the surface of a material.

This invention relates to a process for the treatment of the surface ofa material which comprises treating the surface with a powder ofastatistical copolymer of ethylene and maleic anhydride, having aparticle size of between 0.5a and 400;; and possessing on the surface ofits particles, at least one crosslinking agent for the copolymer whichcontains as reactive groups, one, two, three or four alcohol (OH) groupsand at least one amino or amido group, in an amount from 0.05 to 6reactive groups per anhydride group present in the copolymer and thenbringing the powder to a temperature of between I 10 and 300C.

The copolymers which can be used in the process of this invention areknown and include the binary statistical copolymers obtained in aconventional manner by radical copolymerisation of ethylene and maleicanhydride under high pressure in a stirred autoclave reactor. It is alsopossible to use, instead of the ethylene/maleic anhydride, terpolymerswhich contain, in addition to ethylene-derived units and maleicanhydride-derived units,.a small amount of a third monomer,copolymerisable, by a free radical process, with the other two. Suitablethird monomers include for example, olefines, vinyl derivatives andacrylic derivatives such as propene, isobutene, vinyl acetate, ethylacrylate or methyl vinyl ether.

The most convenient copolymers are the copolymers of ethylene and maleicanhydride (EMA) which contain from 80 to 99 parts by weight of unitsoriginating from ethylene and from 1 to parts by weight of unitsoriginating from maleic anhydride; the grades (melt index) of suchcopolymers generally varies between approximately 0.5 and 3,000.

The copolymers must be used inthe form of powders having an averageparticle size of between 0.5 and 400 t. Such powders can be prepared byany known method, and, of course, the most suitable method will be used.A convenient way of preparing these powders consists of producing themvia an aqueous emulsion of the copolymer. Alternatively, thecopolymermay be ground in known apparatus such as can be usedforgrinding polyethylene.

Thereafter, a good dispersion of the selected crosslinking agent on thepowder must be achieved. Such a dispersion can be effected by any knownmeans, for example by introducing the powder into a suitable aqueousmedium to produce a suspension, and by adding the crosslinking agent tothe suspension. In such a case, the suspension can be used directly forcoating the material. t

The crosslinking agent which is used must contain one, two, three orfour alcoholic OH groups and at least one amine or amide group. It canhowever contain other chemical groups which are unreactive or at mostslightly reactive towards the reactive groups of the copolymer.

Suitable crosslinking agents include the following: monoethanolamine,diethanolamine, methanolamine, l-amino-Z-propanol, 3-amino- 1 propanol,tripropanol- Z-amine, 2-amino'2-methyll ,3-propanediol, 2-ethyl-2-amino-1,3-propanediol, methyldiethanolamine, phenyldiethanolamine,diethylamino-ethanol, Z-amino-lbutanol, dipropanol-Z-amine,alkylpoly-ethanolamines of formula:

where 2n is between 2 and 15, and the R radical contains one to 20carbon atoms, such as Noramox S and S obtainable from Messrs. Prochinor;polyoxyethylenated derivatives of alkylaminotrimethyleneamines offormula;

Mr -i is);

where R is a radical containingbetween one and 20 carbon atoms and n isbetween 1 and 15.

The choice of crosslinking agent will, of course, depend on the intendedend use; thus, for example, the choiceof the crosslinking agent dependson the particle size of the copolymer powder and! on its rate ofdiffusion into the copolymer particles, taking into account the size ofthe particles, the conditions under which the heating of the coating onthe substrate is carried out, and the material of the substrate on whichthe powder is to be used. It has been found that the reagents which canbe used according to the invention do not penetrate into the copolymerparticles before heating and fusion. In contrast, a polyamine which doesnot possess an alcohol group diffuses very rapidly and, throughpremature reaction, leads to the formation of films which arenon-adherent, though partly crosslinked.

Hydroxyethyldiethylenetriamine, which diffuses quite easily, isparticularly suitable for powders of particle size between and4O0;1.Monoethanolamines, diethanolamines and triethanolamines arepreferred for powders of particle size between 0.5 to p" The chemicalreactions which take place are carried out by heating the combination ofsubstrate or material and the powder layer to a temperature of between 110 and 300C, preferably of to 280C, for a period which is generallybetween 10 seconds and 1 hour. The precise temperature and time employeddepends on the desired end use and on the products in question. Theheating can be carried out in various ways. For example, it is possibleto heat the material (or substrate) and to spray the treated copolymerpowder onto its hot surface, or to heat the combination of material andtreated powder after the latter has been applied. It is sometimespossible to subject the-combination of material and treated powder,after heating according to the invention, to an appropriatepost-heating, preferably calised, so as to level the surfaces obtained.It is also possible, according to the invention, to use, instead ofethylene/maleic anhydride copolymers, terpolymers which contain, as wellas ethylene-derived units and between 0.5 and 20 percent of maleicanhydride-derived units, a small amount of a third monomercopolymerised, by a free radical process, with the other two. Such thirdmonomers include, for example, olefines, vinyl derivatives and acrylicderivatives.

The process of the present invention has many useful applications, manyof which are illustrated in the Examples which follow.

In the following Examples which further illustrate the presentinvention, the adhesion was measured by a 180 peeling test in accordancewith Standard Specification ASTM D 903-49. A sheet of glass 105 mm long,25 mm wide and 4 mm thick was bonded to a 200 y. aluminium foil with apolymer powder layer of 100 to 200 u thickness, taking care to introducea mylar tab between the glass and the polymer so as to provide somethingon which to pull.

The powder was obtained directly from a dry mix, or after drying themodified dispersion. The coated aluminium strip can easily be lifted offand folded over to allow part of the uncovered polymer to be introducedinto the jaws ofa tensometer (Lhomargy, pulling speed 100 mm/minute).

The combination was thereafter pressed in a press (pressure 3 kglcmtemperature 165 or 200C,, stoving time 10 minutes unless otherwiseindicated).

identical sandwiches of aluminium (length 105 mm, width 25 mm, thickness2 mm), polymer (100 to 200 11.), and copper or aluminium foil of 200 p.thickness were produced for measuring the adhesion to aluminium, copperand steel and other materials.

EXAMPLE 1 (Comparative) An aqueous dispersion, 50/50 by weight, of apowder, of average particle size 1.5 11., of a copolymer of grade 7.2,containing 2.62 percent of maleic anhydride, is prepared. The viscosityis adjusted by introducing 0.2 percent of hydroxyethylcellulose. A 15011. thick film is deposited on a sheet of glass, on aluminium and on copper by means of a calibrated-face filmograph, and the sample issubjected to a temperature of 200C for 4 minutes. A very poor bond tothe support is obtained, measured to be 0.19 kg/cm on sodium-calciumglass, 0.56 on Pyrex borosilicate glass, 0.51 on aluminium, 0.26 oncopper, 0.73 on steel, 0.26 on Cellophane and 1.70 on Nylon, using thepeeling test described above.

EXAMPLE 2 Example 1 is repeated, but the dispersed medium is modified byintroducing 0.1, 0.25 and 0.5 mol of diethanolamine reagent per mol ofmaleic anhydride in the copolymer. After stoving the sample at 165C and200C, the bond strength to the substrate becomes remarkable.

At a content of 0.5 mol of diethanolamine, the adhesions obtained afterstoving at 200C are 4 kg on sodium-calcium glass, 3.4 on Pyrex glass,0.70 kg/cm on aluminium, 0.376 kg/cm on copper, 2.70 on steel, 0.8 onCellophane and 4 on Nylon. Against this, at a content of 0.1 mol ofreagent, 1.70 kg/cm is obtained on glass, 2 on aluminium and 0.47 oncopper.

Infra-red determinations carried out on the film obtained at 200C, usinga content of 0.5 mol of reagent, indicate that 50 percent of theanhydride groups have been converted into ester-acid and amide groups.The grade of the resin can no longer be measured (less than 0.01) andextraction with boiling xylene yields 58 percent of insoluble matter.

Similar results were obtained under the same conditions with each of thefollowing reagents: triethanolamine, monoethanolamine,dipropanol-Z-amine, diethylamino-ethanol, tripropanol-Z-amine,3-amino-1- propanol, 2-ethyl-2-amino-l ,3-p'ropanediol and 2-amino-Z-methyll ,3-propanediol.

EXAMPLE 3 Example 1 is repeated, but 0.5 mol of phenyldiethanolamine isadded to the polymer dispersion. In the peel test, the film of polymeron glass tears at a force above 3 kg/cm; the adhesion is l.68 kg/cm onaluminium and 0.54 kg/cm on copper.

The adhesion on copper is improved by using substituted diethanolaminederivatives. Comparable results are obtained with methyldiethanolamine,stearyldiethanolamine, and stearylamine condensed with 12 mols ofethylene oxide.

EXAMPLE 4' Example 1 is repeated, but the dispersed medium is modifiedwith 0.5 mol of N,N'-dihydroxyethyldiethylenetriamine per mol ofanhydride in the copolymer. After stoving the sample at 200C, the peelstrength is 0.8 kg/cm on aluminium and 0.7 kg/cm on copper.

EXAMPLE 5 A powder of particle size 2 y. of a copolymer of grade 9.4 andof maleic anhydride content 4.5 percent is modified with 0.5 mol ofoleyl pentaethanolamide per mol of maleicanhydride in the copolymer.After stoving the sample at 200C, the bond strength increases from 0.528kg/cm to 2.6 kg/cm on glass, from 0.5 kg/cm to 2.8 kg/cm on aluminiumand from 0.45 kg/cm to 0.50 kg/cm on copper.

Similar results are obtained with the polyethanolamides of the formula:

0 (CH cH,0) H

in which m n is between 2 and 30 and R is a carbon chain containing fromone to 20 carbon atoms.

The invention can be employed for various and important industrialapplications, some of which are illustrated below:

A. Metal Coating The process according to the invention makes itpossible to produce metal coatings which adhere very strongly, and alsomakes it possible to glue metals of the same nature or of differentnature to one another. Thus, due to the remarkable adhesion achieved byemploying the process according to the invention, it is generally nolonger necessary for the metal surface to be specially treated(degreasing and mechanical or chemical toughening) nor to use a primerwhich provides the bond between the metal and the co-polymer.

Of course, the use of the said primer or the treatment of the surfacesremains a possibility.

The properties of the coating (or of the glue line if the process isused for gluing purposes) are those of a cross-linked or bridgedpolymer. Hence they display certain advantages relative to theproperties of the layers of thermoplastic polymers currently used.

From a practical point of view, the uses of the process according to theinvention with metals allow applications in the following fields:insulating coatings (electrical or thermal), anti-corrosive coatings,metal/- polymer/metal sandwiches which can be used in the automobileindustry, and sound insulation. Examples 6 to 9 illustrate someapplications in this field.

EXAMPLE 6 An ethylene-maleic anhydride (EMA) copolymer of grade 9.4 andof maleic anhydride content 4.5 percent is mechanically ground so as toyield particles of size varying between 70 and 400 u. 0.25 M01 ofaqueous diethanolamine per mol of maleic anhydride in the copolymer isintimately mixed with the powder obtained.

After minutes stoving at 200C in accordance with the test describedabove, the peel strength is 1.8 kg/cm on aluminium and 0.8 kg/cm oncopper.

This modified powder has been applied in accordance with the so-calledflame-spraying method. The powder, propelled by a jet of air in theflame of a blow torch, melts and crosslinks in contact with thepreheated substrate (temperatures of between 150 and 280C). At 150C, atwhich temperature peelable coatings are obtained with the usual resins,very strong, permanent bonds are obtained with the compositiondescribed. This technique has allowed a 5 mm thick lining to be producedby coating and stoving at 150C.

EXAMPLE 7 A dry powder of particle size between 50 and 350 p. of acopolymer of 4 percent maleic anhydride content and of grade 20,-rnodified with 0.5 mol of triethanolamine per mol of maleic anhydride inthe copolymer, allowed adherent coatings of 0.2 mm to 1.5 mm to beproduced by fluidised bed deposition on metal objects of irregularshape. Preheating the substrate to 260C for 6 minutes, followed bysteeping it for 6 seconds in a bath of a powder of average particle size150 a (bed temperature 24C, speed of air blown in 1.6 m/minute) yieldeda very adherent coating of 200 p. after postheating at 240C for a fewseconds.

EXAMPLE 8 Powders modified with 0.5 mol ofdihydroxyethyldiethylenetriamine per mol of meleic anhydride in theco-polymer (particle size between 0.5 p. and 50 u) of grade 10 andmaleic anhydride content 2.8 percent were employed successfully byelectrostatic spraying and by means of a fluidised electrostatic bath.After preheating the metal to 220C, adherent coatings of excellentquality and of thickness between 0.12 and 0.5 mm were produced. Withthese fine powders, it was possible to prepare stable, aqueousdispersions and to coat metal foil (thickness 40 to 80 p.) in accordancewith the technology of liquids. Using knife coating, an aqueousdispersion containing 40 percent of polymer (Brookfield LVF viscosity at6 revolutions/minute, 600 cPs) makes it possible to obtain coatings ofthickness between 0.025 and 0.5 mm at a rate of 300 m/minute.

After evaporating the solvent and passing through an oven at between 120and 240 metal temperature, a strongly adherent coating is obtainedwithin the space of a few seconds.

EXAMPLE 9' Similar results as those in Example 8 were obtained ontreating the metal substrate with a solution of a crosslinking agentbefore depositing the copolymer powder.

Thus, a 50/50 solution of diethanolamine in methano] is sprayed onto analuminium foil. After evaporating the methanol, a 2 a powder of anethylene-maleic anhydride copolymer of grade 9.4 and of maleic anhydridecontent 4.5 percent is sprayed onto the substrate. After stoving at200C, the bond is 3 kg/cm instead of 0.5 kg/cm on an untreated metal.Under the same conditions, a similar powder of polyethylene in place ofthe copolymer forms a very weakly bonded layer (less than 0.5 kg/cm)after stoving.

B. Coatings on Glass The exceptional adhesion of the coatings accordingto the invention to glass makes it possible to use the process toproduce glasses coated with a very thin layer of copolymer, to producelightweight glasses in which the copolymer appears as a reinforcingelement, to manufacture various laminates in which glass plays a part,and to size glass fibres. Examples 10 to 14 illustrate some applicationsin this field.

EXAMPLE 10 On customary sodium-calcium glasses, the peel strength of thecoatings according to the process is 4 kg/cm after stoving at 165C.

A 40 percent strength aqueous dispersion of a copolymer (EMA) of grade 9and .of maleic anhydride content 4.6 percent (particle size 2 1.),containing 0.25 mol of diethanolamine per mol of maleic anhydride in thecopolymer, was sprayedonto a glass container. After stoving, an adherentcross-linked coating of thickness varying between 20 p. and 200 a, whichis very strong, is obtained. The impact strength of the glass increasesby more than percent, and the resistance to internal pressure by morethan 50 percent.

The plastic coating forms a protective layer against abrasion which canoccur during handling, holds together the fragments of glass produced onbreaking a bottle, deadens blows ('2), and resists the increase intemperature and the chemical attack which occur dur ing pasteurisation.The copolymers of grades less than and particle size less than 50g areused preferentially.

EXAMPLE 1 l A glass-polymer-glass laminate: was produced by combiningtwo sheets of glass of thickness 2 mm with a bonding layer consisting oftwo 50/50 dispersions of a copolymer (EMA) (reference product) and a50/50 dispersion (EMA) modified with diethanolamine. A 100 p. coatingwas produced on each sheet of glass by means of the filmograph with a200 a calibrated face, the water was evaporated at 100C, and the coatedfaces were brought into contact and heated in a press at C for 4 minutesunder slight pressure (3 kg). The sandwich obtained with the modifieddispersion is very resistant to immersion in water. In the absence of acrosslinking agent, the layers come apart immediately.

EXAMPLE 12 The dispersion quoted in Example 10 allowed a net of glassfibres to be bonded very efficiently.

lt is also used to coat glass fabrics which can, for example, be used inthe wall covering and upholstery industry, in order to producecombinations such as paper-polymer-glass fabric.

EXAMPLE 13 An aqueous dispersion of an ethylene-maleic anhydridecopolymer of grade 2900, of 10 percent maleic anhydride content,containing 17 percent of solid particles (particle size less than 1 u),and modified by introducing 0.25 mol of diethanolamine per mol of maleicanhydride in the copolymer, was prepared.

The dispersion, diluted to 1.5 percent, is applied to glass so that,after stoving, a thin protective coating of less than one micronthickness is produced. The partially crosslinked and strongly adheringfilm protects the skin of the glass more effectively against all causesof external damage than do the usual coatings (poly- (ethylene oxide)waxes or polyoxyethylene stearate), and the strength of the glass isthereby greatly increased.

To estimate the slip property of the coating, the coefficient offriction of the treated glass is measured by the inclined plane method.

Sliding friction is reduced by half relative to the untreated glass. Theintroduction of diethanolamine into the dispersion hence results in areduction of the coefficient of friction, similar to that of the usualcoatings.

Ethylene-maleic anhydride copolymers of molecular weight between 1,500and 10,000and of maleic anhydride contents greater than 1.6 percent aremore particularly suitable for this use.

EXAMPLE 14 The dispersion containing 17 percent of solid particles,described in Example 13, diluted to percent, is used as a sizing bathfor glass fibres. After evaporating the water and stoving at 165C, thecoating represents about 0.5 to 2 percent by weight of the glass. Theglass fibres thus treated for example reinforce the mechanicalproperties of polyethylene similarly to the reinforcement obtained withfibres sized with the mixture of polyvinyl acetate, fatty amide andvinyltriethoxysilane (conventional sizing), even after storage in amoist atmosphere.

C. Textile Coatings The process according to the invention can be usedwidely in the textile industry. Thus the modified ethylenemaleicanhydride copolymer powders:

a. can be used, in the form of powders of particle size generally lessthan 400 u, to coat fabrics and carpets. The cross-linked polymer layerserves as a reinforcing support (tablecloths, sails or carpets), and asa finishing agent in the production of collars and cuffs. ln laminating,the polymer serves as an intermediate layer between a fabric and a sheetof foam or of jute, and for gluing two different fabrics together (forexample for gluing the lining onto the fabric);

b. can be used, in the form of fine powders of size less than 50 peither dry or wet in the applications quoted above. The powdersfurthermore form an excellent binder in non-woven fabrics of woolviscosecotton-staple rayon-chlorinated acrylic fibrepolyamide; or

c. are used, in the form of ultrafine powders of size less than onemicron, either as a finish or combined with finishing resins(creaseproofing resins) to modify the effects they produce, or in'theafter-treatment of fabrics already treated.

Used as a finish, they generally increase the tear strength and abrasionresistance, and give the fabric a softer handle, a more flexible drapeand a glossy and uniform appearance. Compared to polyethylene emulsions,the crosslinkable EMA dispersions have the advantage of being resistantto repeated washings and drycleanings (as a consequence of thecrosslinking and of the bond to the fibre).

Combined with the measures usually employed to increase the creaseresistance of fabrics, they improve the mechanical properties of thefabrics which have been greatly reduced by the treatment with resinsalone.

In an after-treatment, they possess the property of reducing the feltingand shrinkage of wool and of cotton. Crosslinking after fixing to thetextile fibre is absolutely essential for obtaining the desiredproperty. The crosslinkable EMA dispersions which are capable ofbecoming chemically fixed to the fibre and of crosslinking on contactwith it, prove more effective than the known finishes.

The following Examples 15 to 1 7 illustrate these applications in thisfield.

EXAMPLE 15 A 50 percent strength aqueous dispersion of a powder ofparticle size 2 p, of an ethylene-maleic anhydride copolymer of grade9.4 and maleic anhydride content 4.5 percent is prepared. The Brookfieldviscosity at 6 rpm is increased to 465 cPs by introducing 0.4 percent ofhydroxyethylcellulose HG 15,000 cPs.

A drop of 0.003 cm of this dispersion is deposited by means of amicro-syringe onto two parallel single fibres of regenerated cellulosespaced 0.5mm apart (viscose of 15 denier and of mm length). After dryingthe drop, the sample is subjected to a heat treatment at C for 3 minutesso as to produce a point-bond between the two fibres.

Each of the fibres on either side of the point of attachment is cutflush therewith and the composite fibre is stretched in a tensometer soas to study the fibrebinder behaviour during stretching (lnstron,pulling speed 0.2 cm/minute). This method allows the effectiveness ofthis dispersion as a binder in a viscose nonwoven fabric to be assessed.The fibre slips in the binder under a load of 24 :t 1.5 g; theelongation is 14 to 20 percent; an initially single fibre has a tensilestrength of 25.4 i 1.5 for an elongation of 18.6 percent.

The unmodified EMA copolymer dispersion thus does not restore thetensile strength of a fibre.

By way of comparison, the fibres were g1ued" by means of a commercialproduct sold for this purpose, this being a resin of the acrylic esterlatex type. The tensile strength was found to be 21 i 1.5 g. Withpolyethylene of low density, 18 i 1.8 g was found as a result ofslipping.

9 EXAMPLE 16 Example 15 is repeated, but the dispersion is moditied with0.25 mol of diethanolamine per mol of maleic anhydride in the copolymer(Brookfield LVF viscosity at 6 rpm 545 cPs).

The fibre breaks at loads of 26.6 1*: 1.5 g.

The binder hence restores the initial strength of the fibre.

Similar results were obtained with the following single fibres:polyamide (Nylon 66 of 15 denier and 70 mm length), acrylic (of 15denier and 100 mm length), polypropylene (of 15 denier and 90 mmlength), wool and cotton.

The crosslinkable EMA dispersions were used to strengthen non-woven netsmanufactured by the dry method and by the wet method, and the goodproperties are largely retained after. treatment with a greaseremovingsolvent.

EXAMPLE 17 After crosslinking, the ethylene-maleic anhydride copolymerdispersions constitute excellent non-felting and non-shrinking finishesfor W001.

An aqueous dispersion containing 1 percent ofa 1.5 [L powder of acopolymer of grade 480, containing 8.1 percent of maleic anhydride,modified with 0.5 mol of diethanolamine per mol of maleic anhydride inthe copolymer, is prepared.

A double thickness knitted woollen fabric of size 30 X 40 cm (2 X 36dtex yarns) is immersed in this dispersion for 3 minutes and drained soas only to retain 5 percent of resin.

After stoving at 160C for 3 minutes in a horizontal oven, the surfaceshrinkage of the sample is measured as a function of the number of CUBEXwashes, in accordance with the IWS standard specification. After sevenwashes in the Cubex, the shrinkage is only 5 percent, whilst theuntreated jersey shrinks by 65 percent.

Furthermore, the mechanical properties are improved even after treatmentwith grease-removing solvents.

The chemical bond between the polypeptide chains and the copolymer, andthe crosslinking on contact with the fibre explains the performances ofthe finish.

Copolymers of grade above 100 with various contents of maleic anhydrideare more particularly suitable.

D. Paper The process according to the invention is also of value forincreasing the tensile strength and tear strength of papers andcardboards, preferably through addition to the aqueous dispersion ofpaper pulp.

E. Agglomerates It is also possible to use the process according to theinvention to effect the agglomeration of various particles, such as, forexample, vegetablescrap (wood, shavings, hemp or straw) or of variousfibres (cotton, rayon, Nylon or leather).

We claim:

1. In a process for the treatment of the surface of a 1 0 substratewherein the surface is treated with a powder of a statistical copolymercontaining from to 99 parts by weight of units derived from ethylene andfrom 1 to 20 parts by weight of units derived from 'maleic anhydride andthe powder is brought to a temperature between to 300C to form anadhesive coating, the improvement which comprises treating the surfaceof the substrate with a powder of the copolymer having a particle sizeof between 0.5 1. and 400p and possessing,

in a dispersed state on the surface of the particles, at

least one cross-linking agent for the copolymer containing as reactivegroups one, two, three or four alcoholic --OH groups and at least oneamino or amido group, in an amount from 0.05 to 6 reactive groups peranhydride group present in the copolymer.

2. The process according to claim 1 in which the copolymer contains, inaddition to units derived from ethylene and maleic anhydride, less than10 percent by weight of at least one unit derived from an aolefine orvinyl or acrylic derivative whichcan be copolymerised with ethylene andmaleic anhydride.

3. The process according to claim 1, in which the powder is an aqueoussuspension of copolymer containing the crosslinking agent.

4. The process according to claim 1 in which the powder is brought tothe temperature of between 1 10 and 300C by heating the substrate coatedwith pow der.

5. The process according to claim I in which the substrate is a metal,glass, textile or paper.

6. The process according to claim 1 in which the substrate is in theform of elementary particles which are thereafter agglomerated by thecross-linked polymer.

7. The process according to claim 1 in which the cross-linking agent isdiethanolamine, phenyldiethanolamine, triethanolamine or analkylpolyethanolamide of formula:

where R is a radical containing between one and 20 carbon atoms and n isbetween i and 15.

8. The process according to claim 1 in which the powder is brought tothe temperature of between 1 10 and 300C by pre-heating the substrateand depositing the mixture of copolymer and crosslinking agent on thepre-heated substrate.

9. The process according to claim 8 in which the mixture is deposited onthe pre-heated substrate by spraymg.

10. The process according to claim 1 in which the powder is brought tothe temperature of between 1 10 and 300C by heating the powder andsubsequently coating the substrate with the hot powder.

11. The process according to claim 10 in which the coating is producedby the flame-spraying process.

2. The process according to claim 1 in which the copolymer contains, inaddition to units derived from ethylene and maleic anhydride, less than10 percent by weight of at least one unit derived from an Alpha -olefineor vinyl or acrylic derivative which can be copolymerised with ethyleneand maleic anhydride.
 3. The process according to claim 1, in which thepowder is an aqueous suspension of copolymer containing the crosslinkingagent.
 4. The process according to claim 1 in which the powder isbrought to the temperature of between 110* and 300*C by heating thesubstrate coated with powDer.
 5. The process according to claim 1 inwhich the substrate is a metal, glass, textile or paper.
 6. The processaccording to claim 1 in which the substrate is in the form of elementaryparticles which are thereafter agglomerated by the cross-linked polymer.7. The process according to claim 1 in which the cross-linking agent isdiethanolamine, phenyldiethanolamine, triethanolamine or analkylpolyethanolamide of formula:
 8. The process according to claim 1 inwhich the powder is brought to the temperature of between 110* and 300*Cby pre-heating the substrate and depositing the mixture of copolymer andcrosslinking agent on the pre-heated substrate.
 9. The process accordingto claim 8 in which the mixture is deposited on the pre-heated substrateby spraying.
 10. The process according to claim 1 in which the powder isbrought to the temperature of between 110* and 300*C by heating thepowder and subsequently coating the substrate with the hot powder. 11.The process according to claim 10 in which the coating is produced bythe flame-spraying process.